AbstractFor any scientist working in seismotectonics, the Calabrian Arc represents the most challenging area of Italy. Lying on top of a subduction zone, it is characterised by a complex geological structure largely inherited from the early stages of the collision between the Africa and Eurasia plates. The current and extremely vigorous seismogenic processes, although generated by a mechanism driven by the subduction, are no longer a direct consequence of plate convergence.

About one fourth of the largest Italian earthquakes concentrates in a narrow strip of land (roughly 200x70 km) corresponding to the administrative region of Calabria. The present-day seismicity, both shallow and deep, provides little help in detecting the most insidious seismogenic structures, nor does the available record of GPS-detected strains.

In addition to its fierce seismicity, the Calabrian Arc also experiences uplift at rates that are the largest in Italy, thus suggesting that active tectonic processes are faster here than elsewhere in the country.

Calabrian earthquakes are strong yet inherently elusive, and even the largest of those that have occurred over the past two centuries do not appear to have caused unambiguous surface faulting. The identified active structures are not sufficient to explain in full the historical seismicity record, suggesting that some of the main seismogenic sources still lie unidentified, for instance in the offshore. As a result, the seismogenic processes of Calabria have been the object of a lively debate at least over the past three decades.

In this work we propose to use the current geodynamic framework of the Calabrian Arc as a guidance to resolve the ambiguities that concern the identification of the presumed known seismogenic sources, and to identify those as yet totally unknown. Our proposed scheme is consistent with the location of the largest earthquakes, the recent evolution of the regions affected by seismogenic faulting, and the predictions of current evolutionary models of the crust overlying a W-dipping subduction zone.

AbstractThis work aims at providing an updated and augmented view of present-day tectonics and seismogenic sources of the Abruzzi Apennines, focusing on its extensional domain. This paper was spurred by the 6 April 2009, L'Aquila earthquake (Mw 6.3), an event from which geologists learned important lessons-including rather surprising ones. Although the earthquake was not major compared with other catastrophic events that occurred in Italy and elsewhere, this destructive earthquake led to a thorough review of the geometry - and style, in some instances - that characterises earthquake faulting in this region. The poorly expressed field evidence of the 6 April event, especially in light of the damage it caused in the mesoseismal area, stressed the intrinsic limitation of the earthquake geologists' toolbox.
Abruzzi is the region of a true "seismological paradox": despite the rather long earthquake history available for the region, the number of potential sources for earthquakes of M ≥?6.0 proposed in the literature is two to five times larger than the number of events that appear in the full earthquake record. This circumstance is made even more paradoxical by recent palaeoseismological work that proposed recurrence times of only a few centuries for individual seismogenic
sources. Do the evident faults mapped by previous workers all correspond to potential seismogenic sources?
We aim at addressing this paradox by drawing an updated seismotectonic model of Abruzzi based on the lessons learned following the 2009 earthquake. The model is based on selected geological, geomorphological, seismological, historical and geodetic data and will ultimately feed an updated version of the DISS database (http://diss.rm.ingv.it/diss/).

AbstractSouthern Apulia (Adriatic foreland, Italy), has long been considered a «stable area» lying in between two active orogens, but in fact its tectonic framework is poorly known. To learn more about this topic, we carried out an original structural analysis on Pleistocene deposits. The results indicate that southern Apulia has been affected by mild but discernible brittle deformation throughout the Middle and Late Pleistocene. Joints prevail, whereas faults are rare and all characterized by small displacement. Horizontal extension dominates throughout the entire study area; the SW-NE to SSW-NNE direction is the most widespread. WNW-ESE extension prevails in the Adriatic side portion of the study area, but the dispersion of the measured plane directions is high, suggesting that the local strain field is not characterized by a strongly predominant trend. A Middle and Late Pleistocene, SW-NE to SSW-NNE-oriented maximum extension is not surprising for the study area, as it is compatible with most of the available geodynamic models, whereas the different state of deformation affecting the Adriatic side of the study area requires further investigations. We tentatively interpreted this anomaly as reflecting some regional variation of the general geodynamic frame, for instance as the farthest evidence of ongoing compressional deformation across the W-verging Albanide-Hellenide fold-and-thrust belt.

AbstractWe investigated quantitatively the propagation of a reactivated strike-slip fault through a sedimentary cover. To this end we prepared five simplified analogue models that reproduce a chain with its frontal allochtonous wedge overrunning the foreland. The foreland/chain deformation follows the reactivation of an inherited strike-slip fault cutting the foreland domain. The observation and quantification of the effects of this reactivation, in particular on the orogenic wedge front, provide new insight on the evolution of this type of tectonic setting. We placed special emphasis on quantifying the structural features observed in the models to (1) interpret the kinematics of the reactivated shear zone, and (2) put forward hypotheses on areas indirectly affected by the reactivated fault. The interpretation of the models was based on an integrated analysis of surface and subsurface data. The results show that the geological setting is strongly influenced by the presence of a reactivated pre-existing lineament, that ultimately controls the development and pattern of newly-formed faults. Finally, we present and discuss two natural examples (in Italy Molise-Gondola shear zone, Southern Apennines, and Scicli-Ragusa line, Sicily) in view of the modeling results.